Circuit interrupter



K. ASCHWANDEN CIRCUIT INTERRUPTER Filed's'ept. 19, 1940 wmmvwm Nd .M

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KBMJ Patented May 4, 1943 CIRCUIT INTERRUPTER Karl Aschwanden, Berlin-Wittenau, Germany;

assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 19, 1940, Serial No. 357,350 In Germany September 21, 1939 5 Claims.

rThis invention relates generally to electric eircuit interrupters, and more specically to interrupters in the form of a time lag fuse plug provided with two contacts capable of being separated from each other, and which are under the action of a separating force, such for instance, as a spring. Fuse plugs are known in the art in which two contacts are held together with the aid of solder. If the soldered joint is intensely heated by the electric current the solder fuses and the contacts are separated by the spring.

According to this invention the contacts are held together by friction. The heating effect of the electric current which flows through the contacts eliminates the friction, thereby separating the contacts and interrupting the current.

One object of this invention is to provide a novel circuit interrupter for use in place of a fuse, but which does not employ fusible material for interrupting the circuit.

Another object of this invention is to provide a novel circuit interrupter of the type described which is capable of interrupting the circuit with a time delay inversely dependent on the current flowing in the circuit.

Another object of this invention is to provide in combination with a novel time lag circuit interrupter of the type described, means eiective to substantially instantaneously open the circuit on heavy overloads.

These and other objects of this invention will become more apparent upon consideration of the following detailed description of preferred embodiments thereof when taken in connection with the attached sheet of drawing in which:

Figure l is a longitudinal section of an interi'uptei' constructed in accordance with this invention,

Fig. 2 is a partial sectional view similar to Fig. l but showing a modified form of contact construction,

Fig. 3 is a longitudinal sectional view of another form of interrupter, and

Fig. 4 is a transverse sectional view taken substantially on the line IV-IV of Fig. 2.

In the embodiment of the invention shown in Fig. l, there is provided a hollow casing I of insulating material, preferably a ceramic body,

the lower end of which has a reduced extension z to which is secured a metal bottom cap 2. The cap 2 supports a conductor rod 3 which extends into the cylindrical hollow space 4 of the casing through an aperture in the bottom of the casing.

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ducting material. A helical spring 'I is pressed against the iiange 6 of socket 5 in such a manner that the spring tends to separate the socket from rod 3. A rod-shaped extension 8 integral with the socket serves as a guide and indicator. A flexible conductor I0 extends from the socket 5 to the metal casing cover. Cap 2 and cover 9 may be secured to the casing in any desired manner, such for example as by having the iianges thereof projected into recesses formed in the casing, and being cemented therein as shown at I1.

The socket 5 consists of a material having a high coefcient of thermal expansion, whereas the rod 3 consists of a material of a low coeilicient of thermal expansion; for instance, such as Invar. The heat caused by the current owing through the rod 3 and socket 5 expands the socket to a considerable extent so that the boi'e becomes larger and releases the bolt in the case of a sufficiently intense heat to interrupt the circuit. Both contacts are then separated by the spring.

The embodiment shown in Fig. 2 instead of being provided with the socket 5 has a metal sleeve II, slotted in the longitudinal direction whose members open when heated and release their grip on the bolt 3. As shown in Fig. 4, sleeve II may be of bimetal construction with the inner laminations having a greater coefficient of thermal expansion than the outer lamination.

The two embodiments in Figs. 1 and 2 represent time lag interrupters which are not instantaneously responsive to short circuits. To obtain a fused plug effective on 'short circuits a safety fuse is arranged as will be seen from Fig. 3 in a fuse plug corresponding substantially to that of Fig. 1. Inthe cylindric hollow space 4 of the ceramic body I are provided a plurality of fuse wires I2 stretched between the cover 9 and the flange 6 of socket 5. The space between the cover 9 and a plate I3 of insulating material is filled up in a known manner with sand. Parallel to the fuse wires I2 there is stretched in a known manner a' wire I4 which firmly holds an indicator disk I5. The indicator disk I5 is biased outwardly under the influence of a, helical spring I6. If desired, a socket, such as that disclosed in Fig. 2 of the drawing, may be used in place of the socket 5 in the embodiment of the invention shown in Fig. 3. A

In the embodiment shown in Fig. 3, the friction between the contacts is eliminated by the heat effect on over-currents as before, and when On the rod is tightly pressed a socket 5 of con- 55 spring I opens the circuit, indicator I5 will be moved outwardly by spring I6. On high overloads on the order of short circuits, fuse wires l2 will melt at once, and since wire I4 will then carry all of the current it Will also melt at substantially the same time. This occurs very quickly before the contacts have had time to heat up sufficiently for socket 5 to expand enough to release rod 3, and thereby affords substantially instantaneous protection on such high overloads.

The contacts when cooled may be pressed together so that the interrupter is again ready for use. This may be done in the embodiment of Fig. 1 merely by depressing indicator rod 8, whereas in the embodiment shown in Fig. 3 it would be necessary to disassemble the fuse. In contradistinction to the known fuse plugs operating with solder, no solder is required for the plugs constructed according to this invention,

and no heat is necessary to establish the joint between the separable contacts.

While in the embodiment shown the heat effect is brought about by the current flowing through the socket or the sleeve and the bolt, also a heating coil may be provided which is connected in series to the contacts.

Having described preferred embodiments of the invention in accordance with the patent statutes, it should be understood that the invention is not to be limited to these specic illustrations since it will be apparent to those skilled in the v art that many changes and modications may be made in these specic structures Without departing from the broad spirit and scope of this invention. Accordingly, the invention should be interpreted as broadly as possible and limited only by the prior art and by express limitations contained in the following claims.

What is claimed is:

l. In a circuit interrupter having separable contacts, one of said contacts being rod-like in character,the other of said contacts comprising a unitary substantially cup-shaped socket member including a base and side Walls projecting therefrom toward said rod-like Contact, said side walls being split and normally tightly frictionally receiving said rod-like contact to prevent separation of said contacts, and at least the side walls of' said socket member being of bimetal arranged to deflect outwardly in response to heating thereof to release said rod-like contact and permit separation of said contacts.

2. In a circuit interrupter having separable contacts, one of said contacts being rod-like in character, theV other of said contacts comprising a unitary substantially cup-shapedA socket memt.

ber including a solid base and side walls of bimetal projecting from said base toward said rod-like contact for normally tightly frictionally receiving said rod-like contact to prevent separation of said contacts whereby the side walls of said socket contact member are expansible in response to heating thereof to release said rodlike contact to permit separation of said contacts.

3. In a circuit interrupter having relatively xed and movable contacts, said xed contact being rod-like in character, said movable contact comprising a unitary substantially cup-shaped socket member including a base and side walls projecting therefrom toward said rod-like contact for normally tightly frictionally receiving said rod-like contact to prevent separation of said contacts, at least the side walls of said socket contact member being of bmetal so as to be eXpansible in response to heating thereof to release said rod-like contact to permit separation of said contacts.

4. In a circuit interrupter, an insulating casing having spaced terminals, separable contacts in said casing, one of which is connected with one of said terminals, one of said contacts being rod-like in character, the other of said contacts comprising a substantially cup-shaped socket member for normally tightly frictionally receiving said rod-like contact to prevent separation of said contacts, said socket contact member being expansible in response to heating thereof to release its hold on said rod-like contact to permit separation of said contacts with a time delay action upon the occurrence of light overloads, and fusible means in said casing connecting the other of said contacts to the other of said terminals for relatively quickly interrupting the ircuit upon the occurrence of heavier overloads.

5. In a circuit interrupter, an insulating casing having spaced terminals, separable contacts in said casing one ci which is connected with one of said terminals, one of said contacts being rod-like in character, the other of said contacts comprising a substantially cup-shaped socket member for normally tightly frictionally receiving said rod-like contact to prevent separation of said contacts, said socket contact member being expansible in response to heating thereof to release its hold on said rod-like contact to permit separation of said contacts with a time delay ction upon the occurrence of light overloads, fusible means in said casing connecting the other of said contacts to the other of said terminals for relatively quickly interrupting the circuit upon the occurrence of heavier overloads, and indicating means movably mounted on said casing and movable in response to the interruption of both light and heavy overloads within said casing to an indicating position.

KARL ASCHVVANDEN. 

